Naphthyridine derivatives

Abstract

The present invention provides a 1,8-naphthyridine compound of the formula <IMAGE> wherein R is hydrogen, methyl, ethyl or propyl, and a nontoxic pharmaceutically acceptable salt thereof, and a process for preparing a 1,8-naphthyridine compound of the above formula which comprises (A) reacting a compound of the formula <IMAGE> wherein Y is halogen, lower alkoxy, lower alkylthio, lower alkylsulfinyl, lower alkylsulfonyl, lower alkylsulfonyloxy or arylsulfonyloxy, and R1 is hydrogen or lower alkyl, with a compound of the formula <IMAGE> wherein R2 is hydrogen or a protective group for the amino group, and R is as defined above, and when a reaction product in which R1 is lower alkyl and/or R2 is the amino protective group is obtained, treating it with an acid or base, and/or reductively cleaving it, (B) decomposing a compound of the formula <IMAGE> wherein A (-) is a fluorine-containing anion, and R1 and R2 are as defined above, and when a reaction product in which R1 is lower alkyl and/or R2 is the amino protective group is obtained, treating it with an acid or base, and/or reductively cleaving it, (C) treating a compound of the formula <IMAGE> wherein R'1 is hydrogen or lower alkyl, R'2 is hydrogen or a protective group for the amino group, provided that R'1 and R'2 are not hydrogen atoms at the same time, and R is as defined above, with an acid or base, and/or reductively cleaving it, and optionally converting the resulting compound to a nontoxic pharmaceutically acceptable salt thereof. The 1,8-naphthyridine compound is useful as an antibacterial agent.

What we claim is: 
     
       1. A 1,8-naphthyridine compound of the formula ##STR25## wherein R is hydrogen, methyl, ethyl or propyl, or a nontoxic pharmaceutically acceptable salt thereof. 
     
     
       2. 7-(3-Amino-1-pyrrolidinyl)-1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid or a nontoxic pharmaceutically acceptable salt thereof. 
     
     
       3. A compound according to claim 2 wherein the salt is a hydrochloride. 
     
     
       4. 1-Ethyl-6-fluoro-1,4-dihydro-7-(3-methylamino-1-pyrrolidinyl)-4-oxo-1,8-naphthyridine-3-carboxylic acid or a nontoxic pharmaceutically acceptable salt thereof. 
     
     
       5. A compound according to claim 4 wherein the salt is a hydrochloride. 
     
     
       6. An antibacterial composition comprising as an active ingredient an antibacterially effective amount of a 1,8-naphthyridine compound defined in claim 1 and a pharmaceutically acceptable carrier therefor. 
     
     
       7. A method for treatment of a bacterial infection which comprises administering to a warm-blood animal an antibacterially effective amount of a naphthyridine compound defined in claim 1.